It has been shown that the use of clean air systems in operating theaters dramatically reduces the occurrence of post-operative sepsis. Hence, the use of such systems is regarded as being highly desirable, especially in the case of operations in which body tissues are exposed for long periods of time, as for example in orthopaedic operations, or operations on patients that have deficient immune systems, for example, burn victims.
Conventional clean air systems involve the use of an enclosure that is placed around the operating table and that is supplied with sterile air. Operating staff in the enclosure wear body exhaust suits and full facial masks. Such systems, although effective, have not, however, been widely adopted because their installation and maintenance costs are extremely high and the clothing worn by the operating staff is regarded as being too restrictive and uncomfortable.
A number of alternative, localized clean air systems have been designed but these have also been found to be unsatisfactory in a number of respects. The main problem associated with such systems is that the clean air flow being supplied to the localized site entrains the surrounding unclean air and thus is contaminated by the time it reaches the localized site. Examples of localized clean air systems include devices that rest upon, and are sealed to, the patient's body and which blow clean air across the operative site. Such devices are restrictive to surgery and often fail due to ineffective seals. There are also devices that are suspended above the operating table and blow air downwards onto the operative site.
An example of the latter type of localized clean air system is disclosed in U.S. Pat. No. 3,923,482. The system comprises an air discharge head that is meant to discharge a central column of low velocity laminar flow air surrounded by a sheath of higher velocity air, which is supposed to prevent contaminated air being entrained into the central column. The central column of low velocity air is generated either by inserting a perforated sheet centrally in the airstream to retard the air flowing through it or by channelling the airstream into an outer, annular channel and a central channel, and decreasing and increasing the cross-sections of these, respectively, with distance downstream so as to create the desired velocity profile. In practice, however, both arrangements are unlikely to create the desired velocity profile.
It is an object of the present invention to provide an improved localized clean air system which generates an air flow comprising an inner region of low velocity air and an outer region of higher velocity air.
It is a further object of the invention to provide an inexpensive localized clean air system for use in operating theaters that is not obstructive to surgery, that delivers a clean air flow to the operative site, and that is of comparable efficiency to the conventional, enclosure-type clear air supply systems.